Electric switch mechanism



1958 J. v. s. DAHLGREN 2,859,312 ELECTRIC SWITCH MECHANISM Filed March 15, 1956 ls l8 20 1 I 26 2! i l6 l2 f 1 I l4 22 i S 46 54 56 Q 42 58 49 1 40 I -7 P 1 I I l as f 70 lo 3 J 34 55 L 52 44 so S as ATTORNEY United States Patent,

ELECTRIC SWITCH NIECHANISM John V. S. Dahlgrem'F airhaven, N. 1., assignor to The V Wilcolator Company, Elizabeth, N. J., a corporation of Delaware My invention relates to improvements in electric switch mechanisms, particularly useful for controlling the electric current supplied to air-conditioning units, clothes driers, washing machines, cooking'ranges and other appliances Where high amperages must be carried or where fast and positive contact action is needed.

The control switches now used in appliances of the type referred to above are not entirely satisfactory because the switch contacts often arc and weld together. Considerable effort has been devoted to the solving of the problem of providing a switch mechanism for such appliances which will safely and reliably carry higher currents than heretofore and at such higher currents operate without welding of the switch contacts. One approach to a solution to this problem has'been to mount the movable contacts with spring means interposed between them and their primary support whereby when they are moved into contact withthe fixed contacts the shock force will be absorbed in the spring. Despite such resilient mounting of the movable contacts, however, bounce or chattering of the movable contacts upon striking the fixed contacts has still been found to exist to a degree sufficient to permit arcing and consequent welding of the contacts.

With the foregoing in 'mind, the primary object of my invention is to provide a switch mechanism in which a movable bridge or movable contacts may be snapped onto fixed contacts without bouncing and consequent arcing and welding. I accomplish this broadly by providing means for holding the contacts firmly and continuously together while the shock force resulting from the engagement of the fixed contacts by the movable contacts is absorbed.

Another object of the invention is to provide a switch mechanism characterized by a clean breaking action.

This is accomplished broadly by providing for a levering action on the movable contacts during the initial movement of their support toward open-circuit condition whereby the movable contacts are initially maintained in contact with the fixed contacts while the inertia of the switch arm is overcome and acceleration thereof begun and are then wrenched free of the fixed contacts. i

A further object of my invention is to provide aswitch mechanism particularly useful in connection with snapacting controls, thermostats, relays and other types of switches where a contact bridge or contacts are snapped onto fixed contacts.

In accordance with my invention, I have discovered that previously encountered difiiculties are largely, and may be completely, overcome by providing a switch mechanism comprising a pair of cooperating contact members, an actuating means for efiecting relative movement of the contact members to bring their contact surfaces into and out of engagement with each other to respectively close and open an electn'ecircuit, and leverage means acting to tilt the contact members relative to each other while the contact surfaces are in engagement with each other immediately prior to the movement of the contact members out of engagement with each other by the actuating means. A camming means is also provided in one support for the contact members to shift the contact members and their contact surfaces relative to each other immediately following initial contact thereof in a switch closing operation, whereby at least a portion of the shock is absorbed frictionally. Such camming means in addition provides for further frictional absorption of the shock force in having relatively movable parts which move with respect to and in frictional engagement with each other during the period following initial engagement of the contacts but before the actuating means has come to rest in closed position of the switch. Pivot means may also advantageously be incorporated in one support forthe contact members to permit accurate proportioning of the forces between the contact members. In a preferred construction the contact surface of at least one of the contact members is also arcuately shaped, for example spherical, so that some rolling action is obtained as the contact members, while in contact, are shifted relative to each other.

The improved switch mechanism is adapted to provide a clean make-and-break in an extremely short period of time and, in general, is adapted to be associated with either or both of the fixed or movable contact members of electric switches or controls.

The features of my invention are described more in detail hereinafter in connection with the accompanying drawing forming a part of this application and which shows one embodiment of the improved switch mecha nism.

In the drawings: 7

Fig. l is a broken longitudinal sectional view of a thermostatic control, including a switch mechanism constructed and arranged in accordance with the invention and illustrated in connection with the movable contact bridge of a control switch;

Fig. 2 is an enlarged vertical sectional 'view taken on the line 2-2 of Fig. 4 taken on an enlarged scale;

Fig. 3 is a fragmentary plan view looking down on the movable contact bridge mechanism shown in Fig. 1;

Fig. 4 is an end view of the contact bridge mechanism shown in Fig. 3, looking in the direction of the arrows 44, and

Fig. 5 is a view similar to that of Fig. 4, looking in the direction of the arrows 55 in Fig. 3.

Referring to Fig. 1 of the drawings, the thermostatic control shown therein is arranged to break on a rise in temperature, but the switch mechanism may be used for either make or break on a rise in temperature. The control comprises a casing 10 provided with a cover 12 and a terminal block 14 of insulating material mounted in one end of the casing between the cover and bottom of the casing and secured th'erein by bolts 16, only one of which is shown. A dial shaft 18 for adjusting the control extends through the cover 12 and is threaded into a sleeve 22 rotatably mounted with respect to the cover 12 but which is locked in fixed position by means of a gripping plate 24, normally held tight against the flange of the sleeve 22 by a screw 26. A non-circular washer 19 mounted on the shaft 18 against rotation relative thereto by lugs 19 (only one shown) which enter slots 18 (one shown) of shaft 18 cooperates with a mounting bracket 20 to limit rotation of control stem 18. A spring 21 acts upon the underside of washer 19 to maintain it in contact with underside of bracket 20. Aconventional temperature-responsive diaphragm element 28 is mounted inside the casing and held to the bottom of the casing by means of a nut 30. The element 28'is filled with a temperature-responsive fluid and connected by a filled Patented Nov. 4, 1958 1ever'36 of a snap-acting mechanism of more or less conventional type, including a switch arm 38 to which an insulator 40 is riveted by rivets 42, and an interconnect- =ing load spring 44. The elements 36, 38 and 44 are mounted in a'bracket 46 located in the casing and having spaced side webs 48 provided with pivot projections 49 extending through openings inthe end of the casing 30.

-The lever 36 comprises a webbed member having a central cut-out section for the spring 44 and opposite knife edge shoulders respectively engaging notches at 50 in the bracket side Webs 48. The switch arm 38 includes a central. short tongue member onto which the spring 44 is hooked .and side legs respectively engaging notches at 52 in the bracket side webs 48.

The tensionof the spring 44. holds the knife edges of the lever 36 in the notches Stl-and' the legs of the switch arm -38 in the notches 52 and provides an over-center snapacting mechanism actuated on the one hand by the diaphragm 28 and on the other by a bearing pin 54 mounted in. the lower end of thedial stem 18 and bearing in a recess in the upper central portion of the bracket 46 in offset relation with respect to the pin 34 of the diaphragm member 28. When the diaphragm member 28 expands and moves theend of the lever 36 to a predetermined extent, the switch arm 38 and insulator 40 are snapped downwardly. When the fluid in the bulb connected to the diaphragm member 28 contracts, the switch arm 36 is permitted to move downwardly and the switch arm snaps to its upper position, as shown in Fig.1.

The insulator 40 carries a movable contact bridge assembly 55 which cooperates with a pair of spaced fixed silver contacts 56 riveted to terminals 58 mounted in the terminal block 14 and riveted thereto by rivets 60. The terminals 58 project from the terminal block to provide wire connections in the usual way, as shown in Fig. l. The contact bridge assembly 55 shown in Fig. 1 and illustrated in enlarged detail in Figs. 2 to 5, comprises a central cage 64 mounted directly on the insulator 40 and a metal contact support or bridge member 66 carried by the cage and provided with silver contacts 67 riveted to the ends, of the bridge.

The cage 64- and bridge member 66 are formed of sheet metal, the latter preferably of copper. The cage comprises a base portion 68 resting directly on the member 40 and secured thereto by bent-over retaining members 70 extending through spaced holes 72 in the member 40. The base 68 also includes a central pressed-out spring-bearing recess 74 at an angle of 30 with respect to the base 68 and facing outwardly with respect to the snap mechanism, in the manner shown in Fig. 2. The pressed-out part of the cage forming the spring-bearing recess 74 extends downwardly into an opening 76 in the insulator 40. a

The cage 64 includes an inner, upwardly-projecting leg 78 extending at about right angles to the base 68 and provided with a transverse slot 80, having the shape shown in Fig. 5 to provide upper and lower pivot points. An outer leg 82 extends upwardly and outwardly from the base 68, .on the opposite side of the cage from the leg 78, at an angle of about 65 with respect to the plane of the base 68, and is provided with a transverse slot 84. The slots 80 and 84 are adapted to accommodate and respectively retain centrally-located inner and outer support projections 86 and 88 of the bridge 66. Slot 84 'has a lower edge shaped as shown in Fig. 4 to provide a central pivot point and a straight upper edge to stabilize bridge member 66 when the switch is in open-circuit condition thereby maintaining contacts 67 level for subsequent closing of switch.

The central section of the bridge 66 is formed to provide an annular spring-bearing recess 90, generally facing the recess 74 in the cage 64, except that while the axes of these recesses are generally about parallel they are offset so that the axis of the recess 90 is located inwardly. with respect to the axis of the recess 74. The recess 90 is located in a plane at an angle of about 30 with respect to the central web of the bridge, as shown in Fig. 2. A compression coil spring 92 is mounted between the bridge 66 and cage 64 with its ends respectively located in the recesses 74 and 90 in the manner shown in Fig. 2.

When the contact bridge assembly is biased toward the fixed contacts 56 and the contacts 67 are pressed against the fixed contacts, the relationship of the bridge 66 to the cage 64 is that shown in the dotted line position of the bridge in Fig. 2 with the projection 88 of the bridge resting on the pivot point of the slot 84. When the contacts 67 are out of engagement with the fixed contacts, the bridge and its projections 86 and 88 are in the full line position shown in Fig. 2 with the upper surface of the projection 88 resting against the upper straight surface of the slot 84, so that the contacts 67,- as indicated, are leveled or are equally spaced with respect to the fixed contacts. I

In the operation of the switch mechanism from the open switch position, as represented in Figs. 2 and 4, to closed position, by the snap mechanism shown in Fig. 1 or by some equivalent actuating mechanisn'nthe .body of the bridge and its projections 86 and 88 remain in the full line position shown in Fig. 2 up to the instant that the contacts 67 hit the contacts 56. At that instant the pressure applied to the bridge assembly 55 by the switch arm causes the outer edge of the bridge, including the projection 88, to move downwardly as the, cage for the bridge 66. At the same time the contact bridge is shifted inwardly with respect to the cage, and thecontacts 67 are translated rearwardly and rolled respectively across the surface of the fixed. contacts. This shifting action is caused by the camming action of the outer bridge structure in cooperation with the inclined cam surfaces provided by the leg'82 alongside the ends of the slot 84. For example, Figs. 2, 3 and 4 show the edge surfaces 94 of the bridge 66, on the respective sides of the projection 88 engaging the inner slopping surfaces 96 of the leg 82 at the respective ends of the slot 84. When the contacts 67 are moved to engage the fixed contacts 56, the spring 92 is compressed and the camming action of the surfaces 96' and 94 causes the bodily inward movement of the bridge 66 as the outer portion thereof and the leg 82 move relative to each other; As a result of the foregoing actions, the switch mechanism closes the circuit between the fixed contacts with practically no arcing, bounce or chattering because the shock force is absorbed .frictionally in the relative movement of the contacts 67 and 56, while in engagement, which results from the indicated inward shift of contacts 67, and in the frictional sliding of the camming surfaces 94 and 96 upon one another.

When the bridge assembly is snapped away from the fixed contacts to the position shown in Fig. 4 to leave the bridge in the position represented by the full-line position in Fig. 2, the first action which takes place at. the instant the switch arm starts to move is that the breaking force is applied to projection 86 by the upper edge of slot in arm '78 and bridge 66 becomes a lever pivoting about contacts 67 which are maintained during this initial movement of the bridge assembly in firm con tact with contacts 56 by spring 92. This engagement of contacts 67 with contacts 56 is maintained until the upper straight edge of slot 84 engages the outer end of the tab 88 of bridge 66 and withdraws it and the movable contacts 67 away from contacts 56. The levering action of bridge 66 during this initial movement of the bridge assembly in operation of the switch to open-circuit condition exerts a prying action on the contacts 67 to break any weld that may exist between them and fixed contacts 56. This may be furthered to a small degree also by reason of the fact that spring 92 tends to shift bridge member 66 and hence contacts 67 to the light as seen in Fig. 2 as assembly 55 is moved downwardly.

In this opening operation of the switch the functioning of the switch mechanism is such that the movable contacts are first made free of the fixed contacts, with respect to any Welds which may have been caused by arcing, before the movable contacts are snapped away from the fixed contacts. This results in a clean and instant break.

I claim:

1. An electric switch mechanism comprising a pair of cooperating contact members having cooperating contact surfaces, a support for each of said contactmembers actuating means for effecting relative movement of the contact supports to bring their contact surfaces into and out of engagement with each other respectively to close and open an electric circuit, means for pivotally mounting at least one of said contact supports, means which in all conditions of the switch mechanism bias said pivoted contact support toward and laterally with respect to the other contact support and means for shifting at least one of said contact supports and its contact member relative to the other contact member immediately after movement of the contact surfaces into engagement by said actuating means.

2. An electric switch mechanism as claimed in claim 1, in which the shifting means cooperates with said biasing means for laterally shifting the pivoted contact support and its contact member with respect to the other contact member.

3. An electric switch mechanism comprising a pair of cooperating contact members having cooperating contact surfaces, a support for each of said contact members, actuating means for moving the pair of contact supports relative to each other to bring the contact surfaces into and out of engagement with each other to respectively close and open an electric circuit, and a levering and shifting mechanism associated with at least one of said contact supports for tilting and laterally shifting said one contact support and its contact surface relative to the other contact support and its contact surface while the contact surfaces of said contact members are in engagement with each other respectively immediately after the movement of the contact members into engagement with each other and immediately prior to the movement of the contact members out of engagement with each other by the actuating means, thereby obtaining a clean make and break in the circuit without substantial arcing of the contact members, said lever ing and shifting mechanism comprising a cage, a contact support extending across the cage and carrying said one contact member, pivot means at one side of the cage for pivotally retaining one side of the contact support, means at the opposite side of the cage for retaining the opposite side of the contact support while permitting tilting of the contacting support with respect to the cage, a spring in the cage arranged to bias said opposite side of the contact support away from the cage and toward said opposite side of the cage, and cooperating means carried by the cage and contact support for shifting the contact support with respect to the cage during the tilting of the contact support with respect to the cage.

4. An electric switch mechanism according to claim 3 in which said contact support supports a pair of contact members at its said opposite side, in which there are two contact members for engagement by said two contact members carried by said support, and in which said cage has means for rocking said contact support about an axis perpendicular to a line joining the centers of the contact members which it supports to proportion the forces imposed on said contact members, when in engagement, between them.

5. An electric switch mechanism as claimed in claim 4 in which said cage includes means for maintaining said contact support level when the switch is in open circuit position.

6. An electric switch mechanism comprising two pairs of cooperating contact members having cooperating contact surfaces, a support for each pair of said contact members, actuating means for moving the pair of contact supports relative to each other to bring the contact surfaces into and out of engagement with each other to respectively close and open an electric circuit, a levering and shifting mechanism associated with at least one of said contact supports for tilting and laterally shifting said one contact support and its contact surfaces relative to the other contact support and its contact surfaces while the contact surfaces of said contact members are in engagement with each other respectively immediately after the movement of the contact members. into engagement with each other and immediately prior to the movement of the contact members out of engagement with each other by the actuating means, thereby obtaining a clean make and break in the circuit without substantial arcing of the contact members, and means for equally proportioning the forces imposed on said contact members upon one another when in engagement among said contact members.

References Cited in the file of this patent UNITED STATES PATENTS 1,853,964 Dorgeloh et a1 Apr. 12, 1932 1,854,039 Jones Apr. 12, 1932 2,532,468 Sweger Dec. 5, 1950 2,62 ,630 Eckles ,-.-1--.-.--.--,.--- an, 1 3 

